PYCNOGONIDA 



we shall ;i!mi here mention these genera as the last, and foi the 



the examination <>f the genus Phoxichilidiutn. 



The genus t, which is, together with the subgenera Boreonymphon and Cheetonymphon, 



form, presents bj it-- numerous species and great extension the best opportunity 



n naturalists in these northern countries to make a continuous stud} of the development 



the Pycnogonid larva:. It is also Nymphon grossipcs of which we have the most detailed represen- 



tdj given bj Kroyer, Kundsk. Pycnog. (1845), as ' l ' s ;uS " lm> species I shall use, and, 



with reference to my figures, pLI, Kg. 21 25, give a representation of its development during 



this 



1 >n the preceding figure, pi. I, rig. 20, representing the beginning of the second stage, is seen, 

 the three pairs of embryonal limbs, also the beginning of the two foremost pairs of ambulatory 

 5, though only slightly pronounced; but in fig. 21, which absolutel) belongs to the second stage, 

 the first pair of ambulatory legs arc already much developed, of about the same length as the trunk, 

 and with the last joint well developed to a bent, strong claw with two slender thorns, the auxiliary 

 claws, arising from the dorsal side near the base; the articulation of the leg, however, have not pro- 

 led farther than to five joints exclusive of the claw. The second pair of ambulatory legs have not 

 been developed farther than to form a cylindrical process without any articulation or claw, neither 

 are in the body itself the corresponding segments conspicuous, which latter circumstance, perh 

 may be due to a not quite good preservation. The byssus-gland , however, is now fully developed, 

 and the byssus-thread is distinct!) seen to originate from the middle of the gland. In the following 

 figure, fig---, the fore-end of the larva has been represented much more enlarged to show distinctly 

 the structure of the byssus-gland. In the same figure the yolk-mass in the foremost part of the body 

 Iso seen to consist of small particles (the micromeres?) -mailer than those of the hindmost part (the 

 macromi I which, however, only a small portion has been represented; a particular interspace be- 



tween the two yolk-masses is also distinctly seen. In fig. 23 the larva is represented much more devel- 

 i. but still in the second stage; both the foremost pairs of ambulatory legs are now well devel- 

 i, all nine joints, inclusive of the claw, being well separated, and the two auxiliary claws very 

 large; the third pair of legs are also rather long, four-jointed, but the last joint not yet claw-shaped, 

 and there is no indication of any auxiliary claws; the fourth pair of legs and the hindmost part of 

 the trunk form a solid body, while short curves behind indicate the wanting pairs of limbs; anteriorly 

 in the trunk the transverse-oval eye-knob with indistinct eyes is seen; the byssus-threads are still 

 .2) shows the same larva from the lower side, and it shows how the yolk mass not only 

 fills the whole trunk, but also sends long processes into the three pairs of ambulator; legs. The yolk 

 I by a distinct sheath, seen with special distinctness in the third pair of legs, and forming 

 ; the intestine canal during tin following development Before, on both sides of the pro- 

 the embryonal l< '.ill seen, but the) are now decaying, the matrix, or pulp — as it was 



Id times — shrinking, and being consumed (?). In fig. 25 the embryonal legs have been 

 Qted still more enlarged, by which means also the epidermis of the legs is distinctly seen in 

 v, to the pulp, and where it is seen to have preserved its former size anil firmness, 

 only the point lutermost joint being a little retracted; an even shrinking 01 resorption of the 



